The term "bilious temperament" refers to a state of irritability, bad temper, and ill-temper. The antonyms for this word could include a variety of different emotional states and temperaments. These could include calm, cool, collected, content, serene, peaceful, relaxed, easy-going, happy, and even-tempered. The opposite of a bilious temperament is a state of emotional stability and contentment, where a person is able to maintain a positive outlook on life and keep their emotions in check. This can help to reduce stress, improve mental health, and lead to greater success and happiness in all areas of life.